Morphological and electronic modification of 3D porous nickel microsphere arrays by cobalt and sulfur dual synergistic modulation for overall water splitting electrolysis and supercapacitors

Abstract

Herein, 3D hierarchically porous Co and S co-modificated nickel microsphere arrays developed on nickel foam (NF) substrate (NiCoxSy/NF) are synthesized via a facile template-free electrodeposition protocol in Ethaline-based deep eutectic solvent. The resultant NiCoxSy/NF at optimal incorporating level shows highly efficient electrochemical water splitting performance. The NiCoxSy/NF-based alkaline water electrolyzer requires small cell voltages of 1.57 and 1.63 V to reach 10 and 20 mA cm−2 overall current densities, sequentially, along with robust durability for over 100 h. Density function theory (DFT) study indicates that the synergistic actions induced by the dual-incorporation of Co and S, enabling to optimize the binding energies for water dissociation, hydrogen adsorption/desorption as well as the oxygen-containing intermediates. The NiCoxSy/NF manifests excellent electrocapacitive performance with high capacitance (4964 mF cm−2 at 5 mA cm−2) and well cycling stability (0.4% decay after 5000 cycles) being an electrode material for supercapacitor application. Particularly, an all-solid-state symmetric supercapacitor based on NiCoxSy/NF yields high energy density (48.46 Wh kg−1 at 500 W kg−1) with superior cycling durability (6.2% decay after 10,000 cycles). This study contributes a facile path for the synthesis of hierarchically porous materials and highlights the effect of multielement synergistic modulation to boost the electrochemical activity.